What triggers the contraction of arrector pili muscles, creating goosebumps?

The contraction of arrector pili muscles, which leads to the formation of goosebumps, is triggered by both cold temperatures and emotional responses. When the body encounters cold, the arrector pili muscles contract as part of the body's physiological response to conserve heat. This contraction raises the hairs on the skin, creating an insulating layer of air, which helps to retain body warmth.

Similarly, emotional responses such as fear or excitement can also stimulate the contraction of these muscles. The body's fight-or-flight response, activated during stressful or thrilling situations, can lead to this same reaction, causing goosebumps as a part of the sympathetic nervous system's response.

Therefore, it is accurate to say that both cold temperatures and emotional stimuli can cause the arrector pili muscles to contract, leading to the characteristic appearance of goosebumps. This dual mechanism illustrates how the body responds to both environmental changes and psychological states.